New Delhi: Telecom Watchdog, an NGO on Wednesday came under Supreme Court's  scanner for allegedly interfering with the probe in the 2G spectrum case by giving "clean chit" to former Telecom Minister Dayanidhi Maran.

Maran has been accused by CBI of "coercing" a Chennai-based promoter to sell his stakes in Aircel to Malaysian firm Maxis in 2006.

The apex court sought an explanation within seven days from Anil Kumar, Secretary of Telecom Watchdog, for writing a letter to the CBI and publishing an article in a magazine giving a "virtual clean chit" to Maran.

In the letter, he had turned C Sivasankaran, former Chairman of Aircel, from victim to accused by charging him with cooking the story to extract money from Maxis.

 "After going through the contents of the letter written to the CBI, Kumar, Secretary of the Telecom Watchdog, is directed to show as to under what circumstance he wrote a letter dated February 5, 2012 virtually exonerating Maran and accusing Sivasankaran, who has been shown as victim in earlier applications, within seven days," a bench comprising justices G S Singhvi and K S Radhakrishnan said.

  "What prompted him to publish an article when the matter is before us," the bench observed when the CBI alleged that such conduct of Kumar amounts to interference with the probe in the 2G spectrum scam.

The bench, which took serious note of Kumar's conduct, said "CBI should treat it (letter) as a scrap of paper which is to be thrown in dustbin."

Telecom Watchdog had jointly filed the petition along with another NGO, Centre for Public Interest Litigation (CPIL), and a senior journalist Paranjoy Guha Thakurta

The court noted the submissions of CBI counsel and senior advocate K K Venugopal, who said the bonafide of CPIL and the scribe, was not in doubt but the manner in which Kumar conducted himself showed that his assertion of moving PIL in public interest is "highly doubtful".

He said Kumar, who had earlier alleged that Maran was involved in arm-twisting the Chennai-based businessman in selling his stake to the Maxis, had made an attempt to give clean chit to him by writing letter to the CBI and publishing an article in Magazine -- Telecom Live.

 Venugopal read out the contents of letter to the CBI and said Kumar, who earlier accused the agency of going slow in the probe against Maran was now accusing Sivasankaran of extracting money from Maxis.

 He alleged that Kumar was "subverting" the course of investigation despite a warning by the apex court that nobody should try interfere with the probe.

  Advocate Prashant Bhushan, who is also appearing for the Telecom Watchdog, said Kumar has not informed him about the publication of the article in the magazine and letter to the CBI in which he wrote that there was "no truth of coercion by Maran against Sivasankaran".

In the meantime, hearing on the CPIL's plea seeking to investigate Home Minister P Chidambaram’s alleged role in the 2G scam continued.

Since a new bench has been constituted after the retirement of Justice A K Ganguly, Bhushan narrated the sequence of events relating to the case and the arguments will continue on Thursday.